1. Field of the Invention
The invention relates to touch display device, particularly to a touch display device integrating image display with multi-touch detection.
2. Description of the Related Art
FIG. 1A is a cross-section view of a conventional thin film transistor liquid crystal display (TFT-LCD). FIG. 1B is a zoomed-in view of a portion of a signal layer, a controller, a gate driver and a source driver according to the TFT-LCD in FIG. 1A. FIG. 1C is a zoomed-in view of a portion of a pixel array according to FIG. 1B. Regarding to FIGS. 1A-1C, the TFT-LCD uses an active matrix addressing scheme to update the pixel array.
Referring to FIGS. 1A-1C, a polarizer 183 is disposed below an array substrate 180 and arranged to convert an incident beam of electromagnetic waves (light) of undefined or mixed polarization into a beam with well-defined polarization. A polarizer 173 is disposed above an opposite substrate 170 and arranged to detect the polarization direction of the incident beam after the incident beam passes through a liquid crystal layer 150 and the polarization of the incident beam is rotated. Below the opposite substrate 170 is a color filter 171 and below the color filter 171 is a common electrode 172. The color filter 171 is composed of a red filter layer, a green filter layer and a blue filter layer, representing three primary colors RGB of each pixel. The common electrode 172 is made of an Indium Tin Oxide (ITO) transparent thin film. A backlight module 160 is arranged to increase readability in low light conditions.
A signal layer 181 is formed on the array substrate 180. The signal layer 181 includes a plurality of scan lines disposed almost in parallel with each other and a plurality of data lines disposed almost in parallel with each other to intersect with the scan lines, thereby to form a pixel array. A controller 130 is used to control a source driver 110 and a gate driver 120 through the data lines and the scan lines (For purposes of clarity and ease of description, only three data lines D1-D3 and three scan lines G1-G3 are shown in FIG. 1B) to store image data in each pixel of the pixel array. A TFT (thin film transistor) 115, a liquid crystal (LC) capacitor 116 and a storage capacitor 117 are provided in the vicinity of each point of intersection between the data lines and scan lines. A pixel electrode 116a, a common electrode 172 and a LC layer 150 form the LC capacitor 116. The TFT 115 acts like a switch. When a gate pulse turns on a TFT 115 of each pixel of a specified scan line, display voltages will be stored in a LC capacitor 116 of each pixel. The other side of the LC capacitor 116 is connected to the common electrode 172 serving as a reference voltage for display voltages. The display voltage stored in the LC capacitor 116 rotates the direction of the liquid crystal alignment to change the polarization of the incident light. The display voltage, together with two polarizer 173 and 183, determines the luminance value of the corresponding pixel. The function of the storage capacitor 117 is to assist the LC capacitor 116 in storing charges.
A prior touch display device is characterized as a display device equipped with an additional touch detecting device, thereby reducing its luminance and increasing hardware cost.